Distillation of tar



Dec. 11, 1934. G, 5 MCCLOSKEY.

DISTILLATION OF TAR Filed Aug. 6, 1930 2 Sheets-Sheet l ATTORNEY5 l D:I.

LIKE. I)

Dec. 11, 1934. MCCLOSKEY DISTILLA'IION OF TAR Filed Aug. 6, 1930 2Sheets-Sheet 2 INVENTOR ATTORNEYS Patented Dec. 11, 1934 PATENT OFFICE,DISTILLATI ON OF TAB,

Gregory Edward McCloskey, assignor to The Barrett N. Y., a corporationof South Orange, N. J., Company, New York,

New Jersey Application August 6, 1930, Serial No. 473,329

Claims.

This invention relates to the distillation of tar. More particularly itrelates to the distillation of tar in a current of hot gases in whichheat for the distillation is supplied by the sen- 5 sible heat of hotcombustible gases, and additional heat is supplied by combustion of atleast a portion of the combustible ingredients in the gases. Fresh hotcoal distillation gases may be used, for example, and by, partial orcomplete combustion of the gases heat is supplied to the still inaddition'to the heat of the fresh hot gases. The invention includes boththe process and apparatus for carrying it out.

Coal tar such as coke oven tar or gas house l5 tar and water gas tarcomprise constituents which are readily decomposed at high temperaturesand by distillation according to the usual methods more or lessdecomposition of these constituents takes place. Such decompositiondecreases the yield of distillate oil obtained and increases the freecarbon content of the pitch produced. Such decomposition also results in4 the generation of fuel gases. The distillation of this inventionmay beso carried out as to increase the carbon content of the pitch producedby keeping the tar or the resulting pitch at the high temperaturemaintained in the still for a a prolonged period of time. Or byregulating the distillation so that the tar and pitch remain in thestill but a short length of time, for example several seconds, and byspraying the tar in the still in the form of a fine intense spraywhereby a large surface of the tar is exposed to the action of the gasesso that rapid distillation is effected, the gases are quickly cooled toa temperature approaching the temperature of the tar, and high oilyields will be obtained.

,- The process isadvantageously controlled so that the tar is distilledto obtain high oil yields and a pitch of high melting p int, for example350 or 400 F. or higher. The invention will be describedmore'particularly as applied to the distillation of tar at a coke ovenplant by conveying the coke oven gases resulting from the distillationof the coal to the still, preferably without substantial heat loss.

- By mixing a regulated amount of air with the hot gases and ignitingthe gases so that at least a part of the combustible constituents in the.50 gases are burned the temperature of the gases in the still and theheat available lation are increased. 1 I

Fresh hot coke oven gases and other coal distillation gases compriselight oil vapors and 55 vapors of carbolic and creosote oils, etc.finely for distilsuspended particles of pitch and coal or coke andcombustible gases, viz. methane, etc. By mixing air with these gases ina regulated amount and igniting the gases, all or a part of thesecombustible constituents can be burned before the gases come in contactwith the tarspray. The resulting gases contain carbon dioxide inincreased amount and may contain combustible constituents. Thepercentage of air mixed.,with the gases may be so regulated that only asmall 10 portion or a larger portion or substantially all of thecondensable constituents, as desired, are burned before the gases enterthe still. The air content of the gases is advantageously so regulatedthat there is little or no oxygen in 15 the gases after combustion,although the oxygen content may intentionally be so regulated that thesegases contain oxygen in sufiicient amount to cause a partial burning ofthe tar or pitch in the still for. the purpose of still further rais- 20ing the temperature of the gases.

The amount of combustion may be so controlled that the gases firstcontact with the tar or pitch at a temperature of 1000" C. or 1200 C. orhigher. The still is filled with a fine 25 intense spray of tar or thepitch resulting from distillation of the tar. The walls of the still arecontinually washed with the tar or pitch to prevent the accumulation ofpitch or coke thereon. The spray is advantageously produced 30 byrapidly rotating in the still one or more members of generallycylindrical contour at a high rate of speed in such a way that they dipto but a slight extent into a body ofthe tar. or pitch maintained in thebottom of the 35 still and throw a fine intense spray of tar or pitchinto thegases which fills the entire vapor space of the still. Aroll'with a smooth cylindrical surface or a grooved or fluted roll or aplurality of I discs closely spaced on'a shaft may 40 be employed forthis purpose. With a smooth cylindrical roll twelve inches in diameter aspeed 01 900-1200 R. P. In. is sufilcient to throw a fine intense spray01' tar and fill a still of several square feet cross-section. 7

The tar to be distilled may be raw tar containing a small percentage ofmoisture or it may be dehydrated tar or a partially distilled tarorsemi-pitch. The tar may be coke oven tar, gas house tar, low temperaturecarboni-. zation tar, water gas tar, etc. Tar is used gen- .erallyherein to include all grades of tar.

The tar m y be fedinto the still at the same end at which the hotgasesenter so that the gases and flow thru the stillin a generallyconcurrent direction of the tar and gases may enter opposite ends of thestill and flow thru the still in a generally countercurrent direction.Where pitch of high carbon content is desired, countercurrnt flow isordinarily advantageous. Where countercurrent flow is employed the pitchwill leave the still at a higher temperature, the free carbon contentwill be somewhathigher and the oils remaining in the pitch will be ofsomewhat higher boiling range than is the case with countercurrent flow.

The spray of tar and pitch maintained in the still is so intense thatwhen the gases entering the still contain fine particles of pitch orcoke, etc. in suspension such as are present in coke oven gases, forexample, these suspended particles will be removed from the gases in thestill and the gases leaving the still will be substantially free fromsuspended particles except for particles of the spray which may becarried forward with the gases. Such entrained particles may be removedin a settling tower or by baflles or by electrical precipitation, etc.,and such removal is advantageously carried out at a high temperature sothat upon subsequent condensation clean oils will be produced.

The gases enter the still at a temperature sufr'iciently high to cokethe tar. The flne intense spray of tar promotes rapid distillation andthe gases are so rapidly cooled that coking v of the tar is reduced to anegligible amount;

' particles.

the gases usually leave the still at such a low temperature that theymay be broughtinto further direct contact with tar without anysubstantial decomposition of the tar. In order to utilize the heat inthe gases leaving the still it is ordinarily advantageous to partiallydistill the tar, using this heat, before the tar enters the still and isbrought into direct contact with the high temperature gases. For thispurpose a tar spray free from particles of such small dimension thatthey will be carried forward in the gases may be employed and thisspraying may be such as to remove or aid in the removal of entrainedspray particles from the gases leaving the still. The gases mayadvantageously be passed from the still up thru a baflle tower intowhich the tar is sprayed and the tar in washing down over the balll'esis distilled and removes entrained particles of flne spray from thegases so that the gases leaving the baflle tower are substantially freefrom entrained Tar which has been partially distilled in this tower isthen fed directly into the high temperature still for distillation topitch.

In carrying out the distillation in combination with a coke oven batteryit isadvantageous to maintain the still under a partial vacuum in orderto prevent loss thru leakage of coke oven gases from the still and toprevent contamination of the air with such gases. Although a highervacuum may be employed to aid in the distillation, a low vacuum or aninch or two of water is sufilcient to prevent loss of gases thru leakagefrom the still. When the still is operated under a vacuum, the air forcombustion of the gases is advantageously admitted into the gas mainthru one or more apertures which are preferably equipped with valvemeans to control the amount of air blended with the gases. The processmay, however, be carriedout under pressure; that is, the pressure withinthe combustion chamber, the distillation chamber, etc. maybe above thatof the atmosphere, air or other oxygen-containing gas being fed to thesystem under a suitable higher pressure.

The gases resulting from the combustion which may, and which generallywill, contain a considerable percentage of combustible constituentswhich are not burned, will then pass thru the still to efiect the hightemperature distillation and will then pass on thru a settling cham-'ber or ba'flling means, etc. for removal of entrained spray andpreferably for further distillation also, and then to condensers. Theexhauster is advantageously situated beyond the condensers. Afterpassing thru the exhauster the gases may pass thru suitable means forthe recovery of ammonia and light oil, etc.

'A separate chamber may be provided for the combustion of the gases andin this case it is I This pipe and the still, etc. areadvantageouslyheavily insulated.

Safety devices such as wire screens, explosion doors, etc. may beprovided.

In the drawings the invention will be described more particularly asapplied to the distillation of coke oven tar at a coke oven battery butit is intended and is to be understood that the invention is not limitedthereto. Other tar may be distilled and other hot combustible gases maybe employed for the distillation.

Fig. 1 is a plan view of a coke oven battery equipped with a still forcarrying out this invention;

Fig. 2 is an elevation thru the still and hot gas header shown in Fig.1;

Fig. 3 is a section on the line 3-3 of Fig. 2;

Fig. 4 shows a blower for supplying air to th still; and 1 v Fig. 5shows a modifled'form of still.

The coke oven battery 5 is equipped in the usual way with a collectormain 6 and cross- -over main 7. The gases from the individual ovens passup thru the uptake pipes 8 and enter the collector main 6 thru thegc-ose-necks 9.

pipes9, the gases from these ovens may be directed either thru thecollector main 6 to the usual condensers or thru the hot gas header 11into the still 14.

Three or four or more ovens, for example as many as five or six oreight, may be connected to the still. It is advantageous to pass the"gases from a number of ovens into the still since the gases from asingle oven vary in temperature, composition and amount during thecoking of a single charge of coal, and by blending the gases from anumber of ovens a gas stream of relatively uniform composition, etc. maybe obtained.

From the still the gases and vapors pass up thru the baflle tower orsaturator 15. The

drawings show two sets of baflles 16 and 17in the saturator. The tar issprayed into the gases from the spray nozzle 18 situated between thebaflies. It flows down over the baflles 16 and is collect d. at thebottom of the saturator and thru the cooling coil 21.

tillation and the construction and operation of this condenser 20, etc.,may be so regulated that the oil which condenses from the gases in thispreheater is suitable for sale directly as creosote oil. The oil isdrawn oil from the preheater into the storage tank 22 or may be run bymeans of line 22 to decanter 25. From the preheater the gases pass tothe condenser 23. This condenser is sprayed with water or ammonia liquorthru the line 24. The condensate and ammonia liqnor are drawn off to thedecanter 25. The oil, which is carbolic oil, is drawn oflf into the tank26. Ammonia liquor is collected in the tank 2'7. From the condenser 23the gases pass thru the line 28 to means for the recovery of ammonia,

etc. The light oil present in the gases coming from the ovens is largelyor entirely burned before the gases enter the still. The gases leavingthe condenser 23 may contain light oil from'the distillation of the-tarin suflicient quantity to warrant treatment of the gases in a light oilabsorber. v

The still may be five or six feet long and measure two-and-one-half orthree feet in cross-section. A smooth cylindrical roll 12" in diameterrotated at a speed of 900-1200 R. P. M. throws a fine intense spray oftar which substantially fills the entire vapor space of the still andwashes all the interior walls of the still and may advantageously beemployed for distillation according to this invention.

Such a roll is shown at 29. A motor'is indi-- cated at 30. The roll isadvantageously rotated in the direction indicated by the arrow. Thedirection of rotation may be reversed but rotation in the reversedirection increases the power consumption.

The exhauster 31 draws the hot coke oven gases from the selected ovensof the battery the hot gas header into the still. In'the hot gas headernear the still is an opening 32. This opening may be used from time totime to gainaccess to the header for the removal of any coke which mayform and collect in the header. Another opening 33 is provided for thesame pmpose. Air for combustion of the gases may be drawn into thesystem thru either or both of these openings or preferably thru anotheropening provided especially for this purpose. In the drawings the pipe34, which is attached to the cap on the opening 32, is provided for the'admission of air for admixture with the coke oven gases. A valve 35 isprovided to adjust the amount of air admitted into the system. The airmixes with the gases in a regulated proportion.

The amount of air passing thru the pipe 34 may be regulated by anysuitable method. The header 11 may, for example, be maintained underconstant suction by the exhauster 31 so that regulated quantities of aircan be fed into the system thru line 34 and valve 35 by virtue .018 thedifi'erence in pressures between the header 1!.

and the atmosphere. or the air may be supplied under pressure byapparatus such as that shown in Fig. 4 according to which air issupplied thru the pipe 34a from a suitable blower 60 of such capacitythat the desired quantity ofair may be had by adjustment of valve 35aand the by-pass valve in the pipe around the blower 60. The

combustion gases and unburned coke oven gases,

if there be any gases which are not burned, are brought into contactwith the fine spray of tar in the still and the heat of these gasesefiects the distillation. The combustion may take place entirely in theheader, which then constitutes a combustion chamber for the coaldistillation gases. before the gases enter the still thru the opening 36or some combustion may take place within the still, a portion of thestill itself serving as part of the combustion chamber. The tar "spraymay actually contact with the flame. The

spray is a fine intense spray which exposes a large surface of the tarto the distilling action of the hot gases and the tar is rapidlydistilled.

The operation may be controlled to produce a pitch of desired meltingpoint. The flow of tar and air for combustion may be so regulated as toaccomplish only partial distillation and the production of a relativelylow melting point pitch, for example a pitch suitable for road tars. Apitch of higher melting point may be produced, for example a pitchmelting at 350 or 400 F. or higher, by restricting the tar supplied tothe preheater 21; or the amount of air fed into the header by means ofthe pipe 34 may be increased without varying the amount of tar fed tothe 'preheater; or both the tar feed and the air flow may be regulatedto give pitch of the desired melting point. The free carbon content ofthe pitch produced may be regulated by controlling the time during whichthe material being distilled is maintained at a high temperature and byregulating the temperature. Pitch oi high tree carbon content may beproduced if desired.

Thev pitch produced is drawn oil from the still the pitch trap 37 bymeans of the levelling arm 38. By adjusting the position of thislevelling arm the depth of the tar and pitch in the still is controlled.The pitch produced may be treated in any desirable way.

/ It may be blended with other bituminous material or where a highmelting point is produced it may be separately collected and hardened.Where, for example, pitch of 350 F. melting point or higher is produced,the pitch may be drawn on into a trough shown at 39 in the drawings andbe sprayed with a jet of water from the-line 40. The pitch may bechilled and granulated in this way and the hardened pitch is thencollected in the bin 41.

Fig. shows a slightly modified form of still 14a. The'gases enter fromthe header 11a. in the manner indicated in the previous figures and theyleave thru the saturator a to condensers, etc. The tar which is sprayedinto the gases thru the nozzle 18a in the saturator is partiallydistilled in the saturator and the residue flows thru the pipe '19:; tothe still but it enters the still at the end opposite to that at whichthe gases enter so that the gases and tar flow thru the still in acountercurrent direction. YThe pitch which is formed is drawn off thruthe coke trap 3'la'into the bin'41a in the manner described inconnection with the pre- Using the gases from three ovens producing 40tons of coke per day from coal averaging 5% water, and burningsuflicient of the combustible constituents so that the gases are raisedto a of 1050 C. before they are brought into contact with the tar,10,000 gallons of ordinary raw coke oven tar may be distilled 'to pitchwith a melting point of 3'75 or 400 F.,

yielding approximately 75% of distillate oil. The temperature, volumeand composition, of coke oven gases is not uniform from all ovens andthe composition of coke oven tar is not uniform so that results may varyover a considerable range.

Various modifications may be made and safety devices not shown may beprovided to insure safe and efiicient operation all within the scope ofthis invention.

I claim:

1. The method of distilling tar which comprises collecting fresh hotcoal distillation gases from the ovens or retorts of a coal distillationplant, burning a portion of these gases while they are still at a hightemperature after their production, and still contain tar constituentsin vapor form, blending the resultant hot combustion gases with anotherportion of the coal distillation gases which are still hot after theirformation so as to produce blended gases of higher temperature than saidcoal distillation gases, bringing the blended gases into contact withtar so as to distill 01f oils therefrom and then cooling the resultantgas and vapor mixture to form a distillate containing both constituentsoriginally present in the tar distilled and constituents originallycontained in the hot coal distillation gases.

2. The method of distilling tar, which com-' prises collecting freshcoal distillation gases while they are yet at a high temperature aftertheir formation and still contain tar constituents in vapor form,burning only a portion of the gases and blending the resultantcombustion products with the balance of the gases so as to produceblended gases at a temperature above the temperature at which the coaldistillation gases left the ovens, bringing tar into contact with theblended gases so as to distill the tar with the gases while they are ata temperature above that at which they left the ovens, and cooling theresultant gas and vapor mixture so 'as to form a distillate comprisingoils distilled from the tar and oils originally contained in the gases.

3. The method of distilling tar to pitch, which comprises burning aportion of the fresh hot coal distillation gases from a coke ovenbattery so as to keep the gases above the temperature at which theyleave the coke ovens and then distilling tar to pitch by bringing itinto contact with the hot gases in the form of a fine intense spraywhile the gases are still at a temperature above that at which theyleave the coke ovens.

4. In combination with a coke oven battery a tar still, means forintroducing tar into the still, means for producing a fine intense sprayof tar in the gasesin the still, means for withdrawing pitch from thestill, a combustion chamber, means for collecting gases from ovens orretorts of a coal distillation plant and introducing them into thecombustion chamber, means for introducing oxygen into the combustionchamber, and means for conveying gases from the combustion chamber tothe still.

5. In combination with a coke oven plant a tar still, means in the stillfor producing a fine intense spray of tar in the gases therein,insulated means for passing fresh hot gases from ovens of the plant tothe still and having a portion thereof adapted for the combustion of thefresh hot gases therein, and means for introducing a combustionsupporting gas into said insulated means.

GREGORY EDWARD MCCLOSKEY.

